NEW YORK (Reuters) – An investigation commissioned by New Jersey Governor Chris Christie into the “Bridgegate” scandal on Thursday cleared the potential Republican presidential contender of wrongdoing and blamed key staffers for orchestrating the massive traffic jam.

The internal review was conducted by a law firm hired by Christie, whose top staffers have been accused of planning the traffic tie-up at the George Washington Bridge in September 2013 as political payback after Mayor Mark Sokolich of Fort Lee, New Jersey, declined to endorse Christie’s re-election.

“What we found was that Governor Christie had no involvement in the decision to close these lanes and no prior knowledge of it,” said attorney Randy Mastro of the law firm Gibson, Dunn & Crutcher, which was hired to conduct the investigation.

“Not a shred of evidence of it,” Mastro told a press conference in New York.

The report says it did not interview the staffers allegedly involved. New Jersey lawmakers and the U.S. Attorney’s office in New Jersey are undertaking parallel investigations into the traffic tie-up.

The 344-page report said the two-month internal investigation involved 250,000 documents and 70 interviews, but excluded some of the main players in the scandal, such as Bridget Anne Kelly, the governor’s former deputy chief of staff, and Bill Stepien, Christie’s former campaign manager.

The internal report has no legal weight and is eyed with suspicion by many critics because it was ordered by Christie, who in January fired the staffers and denied any involvement.

“Governor Christie’s account of these events rings true. It is corroborated by many witnesses, and he has conducted himself at every turn as someone who has nothing to hide,” the report said.

Instead, blame for the traffic nightmare lies chiefly with Kelly and David Wildstein, a Christie appointee to the Port Authority of New York and New Jersey, which oversees the bridge, the report said.

“(Kelly and Wildstein) knowingly participated in this plan to realign toll lanes leading onto the George Washington Bridge at Fort Lee, at least in part, for some ulterior motive to target Mayor Sokolich,” the report said.

Also blamed were Stepien and Bill Baroni, then deputy executive director of the Port Authority.

“(Stepien and Baroni)knew of this idea in advance, but we found no evidence that they knew of the ulterior motive here, besides the claimed purpose of conducting a traffic study,” the report said.